Flat, multiconductor flexible cable has come into extensive commercial use. Such cable generally comprises a ribbon of insulative material encasing a plurality of round or thin flat conductors disposed in spaced, parallel relation. In many applications, these conductors are electrically shielded to reduce cross-talk, and to reduce electromagnetic interference (EMI) and radio frequency interference (RFI). One or more of the spaced parallel conductors may be in engagement with the ground shield for use as ground conductors in the electrical cable. In order to mass terminate the conductors of the electrical cable, it is necessary to strip away the outer jacket of the cable and the ground shield so that a mass termination connection may be applied to the enclosed conductors.
Strippable, shielded electrical cables for mass termination are known. One example is shown in U.S. Pat. No. 4,513,170, issued Apr. 23, 1985 and assigned to the same Assignee as the present invention. In this prior strippable shielded electrical cable, a release sheet is disposed between the insulative casing that surrounds the conductors and a wire mesh ground shield. A plurality of apertures is placed in and along the release sheet to enable the insulative casing to lightly bond to the outer cover through the wire mesh ground shield. While this cable assembly provides for ready stripping, it has been observed that where the areas of insulation are bonded through the apertures in the release sheet, the cable assembly exhibits some bubbling or separation therebetween.
In an effort to overcome this difficulty, a strippable, shielded electrical cable as shown in U.S. Pat. No. 4,698,457, issued Oct. 6, 1987 and assigned to the same Assignee as the subject invention, has been developed. In this cable, and similar to that shown in the '170 patent, a release sheet is disposed between the casing surrounding the electrical conductors and the wire mesh ground shield. However, in the '457 cable, the apertures have been removed from the release sheet and instead a coating of adhesive is disposed on the upper surface of the release sheet, the adhesive being bonding through the wire mesh to the outer cover of the cable. The lower surface of the release sheet includes a release agent thereon by which there is little or no bonding between the release sheet and the insulative casing. Again, while this construction facilitates stripping, it has been found that the ground shield tends to separate from the casing during bending or rolling operations which subsequently causes difficulty with laying the cable flat during use.
A further example of a known strippable electrical cable is shown in U.S. Pat. No. 4,678,864, issued on July 7, 1987. In this cable, a metallic mesh ground shield is positioned between the main cable and the insulative covering. Portions of the lower surface of the insulative covering are coated by a release agent and other portions of that surface are uncoated. Accordingly, upon application of heat and pressure the insulative covering is bonded to the insulation of the main cable at the uncoated portions in a manner to minimize adhesion and facilitate separation of the main cable from the ground plane.
In addition to the desirability of providing an electrical cable that is readily strippable and yet maintains its structural integrity during handling and use, it has also become desirable to locate the ground conductors or drain wires in any position in the cable. For example, in the '170 cable and the '457 cable constructions, the drain wires are shown as being located at the marginal edges of the cable. Such location helps to facilitate stripability by the use of non-adherent insulative strips located at the marginal edges of the cable. In the '864 cable, the drain wire is also shown as being at the marginal edge of the cable. Accordingly, provision of a strippable, electrical cable wherein the drain wire is disposed at any location throughout the cable is desirable.